Size Can Matter: Improving Metadata Performance with Ext4 Journal Sizing – Part I

An aspect of file system or storage performance that may be overlooked is metadata performance. This is the performance in creating and removing files and directories, updating metadata information, and other aspects of file systems that don’t involve actual data transfers. In a previous article we saw that metadata performance did not change appreciably regardless of whether the journal device was on a ramdisk, a separate disk, or on the same disk as the file system. However, the journal size in that article was only 16MB for a 500GB file system (0.0032% of file system size). This seems to be a fairly small size and could potentially have an impact on metadata performance.
In this article the journal is placed on a second hard drive and its size is varied to understand the impact on metadata performance measured by the metadata benchmark fdtree…